Method of forming all skin viscose rayon



United States Patent METHOD OF FORMING ALL SKIN VISCOSE RAYON No Drawing. Filed Apr. 20, 1959, Set. N 0. 807,298 16 Claims. (CI. 18-54) This invention relates to the production of shaped bodies of regenerated cellulose from viscose and more particularly to filaments and fibers of regenerated cellulose from viscose.

. In the conventional methods of producing shaped bodies of regenerated cellulose from viscose, a suitable cellulosic material such as purified cotton linters, wood pulp, mixtures thereof, and the like is first converted to an alkali cellulose by treatment with a caustic soda solution and after shredding the treated cellulose material, it is allowed to age. The aged alkali cellulose is then converted to a xanthate by treatment with carbon disulfide. The cellulose xanthate is subsequently dissolved in a caustic soda solution in an amount calculated to provide a viscose of the desired cellulose and alkali content. After filtration, the viscose solution is allowed to ripen and is subsequently extruded through a shaped orifice into a suitable coagulating and regenerating bath.

In the production of shaped bodies such as filaments, the viscose solution is extruded through a spinneret into a coagulating and regenerating bath consisting of an aqueous acid solution containing Zinc sulfate. The filament may subsequently be passed through a hot aqueous bath where it is stretched to improve its properties such as tensile strength. The filament may then be passed through a dilute aqueous solution of sulfuric acid and sodium sulfate to complete the regeneration of the cellulose, in case it is not completely regenerated upon leaving the stretching stage. The filament is subsequently subjected to Washing, purification, bleaching, possibly other treating operations and drying, being collected either before or after these treatments.

The filaments as formed by the conventional methods, consist of a skin or outer shell portion and a core portion with a sharp line of demarkation between the two. The cros-section of the filaments exhibits a very irregular or crenulated exterior surface when even small amounts of Zinc salts or certain other polyvalent metal salts are present in the spinning bath. The skin and core portions of the filament represent difierences in structure and these different portions passes different swelling and staining characteristics, the latter permitting a ready identification of skin and core. The sharply irregular and crenulated surface structure has a relatively low abrasion resistance and readily picks up foreign particles such as dirt. Although the core portion possesses a relatively high tensile strength, it has a low abrasion resistance and a low flex-life, is subject to fibrillation and is relatively stiff.

In Patent No. 2,792,281, granted May 14, 1957, there is disclosed the use of di-N, B-hydroxyethyl ethylene diamine for improving the properties and characteristics of shaped bodies of regenerated cellulose. This substance may be considered as an ethylene oxide adduct of ethylene diamine containing 4 ethylene oxide units per molecule of ethylene diamine where theoretically one ethylene oxide unit has reacted with each of the amino hydrogen atoms to form a hydroxyethyl group or radical.

It has been discovered that the adducts containing more than about 4 and less than about 28 ethylene oxide units per molecule of ethylene diamine are not satisfactory for the purposes of the invention disclosed in the aforementioned application or for the purposes of this invention.

It has now been discovered that the presence in viscose of small amounts of water-soluble, water-dispersible alkylene oxide adducts of ethylene diamine, wherein the adduct contains at least about 28 alkylene oxide units per molecule, and, under some conditions, in both :the viscose and the spinning bath, results in the production of shaped bodies of regenerated cellulose such as filaments, films, sheets and the like having improved properties and characteristics and having an enhanced or increased proportion of skin, and, under certain specific conditions, results in products consisting substantially entirely of skin providing that the amount of the adduct is maintained with certain limits and the composition of the spinning bath is maintained Within certain composition limits which will be defined hereinafter. The most readily distinguishable characteristic as compared to conventional filaments include a smooth, non'crenulated surface and the filaments consists of at least skin and in many instances entirely of skin.

This invention contemplates the use of alkylene oxide adducts of ethylene diamine having at least about 28 to about alkylene oxide groups per molecule, preferably from about 32 to about 60 alkylene oxide units per molecule of the ethylene diamine. It is obvious that for all practical purposes considering cost, ease of preparation, commercial availability and solubility in water, in alkali solutions and in acid solutions, the ethylene oxide adducts are preferred and the invention is described with this species although the corresponding propylene oxide adducts also are satisfactory.

Theoretically, adducts containing 28, 32, 60 and 100 alkylene oxide units per molecule of ethylene diamine, for example, would have polyoxyalkylene groups containing 7, 8, l5 and 25 alkylene oxide units, respectively, reacted with each of the amino hydrogen atoms. It is to be understood that for the purposes of this invention each of the chains of alkylene oxide units need not be identical.

The term adduct is used herein and. in the claims in its normal sense to designate the reaction or the addition product formed by the reaction of an alkylene oxide or a polyoxyalkylene glycol with ethylene diamine wherein, as stated above, a polyoxyalkylene glycol radical replaces each of the amino hydrogen atoms. These adducts or ethylene diamine derivatives may be represented by the following structural formula:

where A is H or CH m, n, x and y are whole numbers and their sum is at least 28 to about 100, preferably from about 32 to about 60.

The production of products having increased proportions of skin or substantially all skin requires that certain minimum amounts of the alkylene oxide adduct be in solution or be dispersed in the viscose and that under some conditions also in the spinning bath. The adduct may be conveniently added to the viscose in the form of a solution or dispersion in alkali or water and to the spinning bath in a solution or dispersion of water or of the spinning bath.

The alkylene oxide adduct of ethylene diamine is added to and incorporated in the viscose in an amount of at least about 0.25 by weight of the cellulose in the viscose and may vary up to about 4%, preferably, the amount varies from 0.5% to 3%. Lesser amounts do not result in the production of products consisting entirely of skin and greater amounts affect adversely the physical properties of the products. Amounts within the preferred range are most effective in enhancing the characteristics and properties of the products. The adduct of ethylene diamine' may be added at any desired stage in the production of the viscose such as in the preparation of the refined wood pulp for the manufacture of viscose, before or during the shredding of the alkali cellulose, to the xanthated cellulose while it is being dissolved in the caustic solution or to the viscose solution before or after filtration. The adduct is preferably added after the cellulose xant-hate has been dissolved in the caustic solution and prior to filtration. a

The viscose may contain from. about 4% to about 9% cellulose, the particular source of the cellulose being selected for the ultimate'use of the regenerated cellulose product. The caustic soda content may be from about 4% to about 11% and the carbon disulfide content may be from about 30% to about 60% based upon the weight of the cellulose. The modified viscose, that is, a viscose containing a small amount of the adduct, should have a sodium chloride salt test number above about 7 and preferably about 9 or higher at the time of spinning or extrusion. The salt test is an indication of both the amount of carbon disulfide added to the viscose and the degree of aging. The sodium chloride salt test number is the minimum percent concentration of sodium chloride solution at 18 C. required to coagulate 3 drops of viscose. It is determined by dropping the viscose into a beaker containing about 40 cc. of sodium chloride solution at 18 C. while stirring. Stirring is continued for 90' seconds after the last drop of viscose has been added.

In order to obtain the improvements heretofore mentioned, and particularly to obtain all skin, or substantially all skin yarn with their resulting advantages, it has been found that in addition to the polyoxyalkylene oxide adduct, the amount of carbon disulfide used in the preparation of the viscose and the acid and zinc contents of the acid spinning bath are important. The presence of the modifier of this invention in a viscose of required carbon disulfide content combined with these spinning baths results in the production of yarns of improved properties such as high tenacity, high abrasion resistance, high fatigue resistance and consisting of filaments composed substantially or entirely of skin.

In practicing the present invention, the carbon disulfide added in preparing the viscose should be at least 30%, based on the bone dry cellulose content, and preferably in the order of 35% to 50%.

Also, generically and in terms of the industrial art, the spinning bath used in the practice of the present invention is a low acid-high zinc spinning bath. The bath should contain from about 10% to about 25% sodium sulfate and from about 3% to about zinc sulfate, preferably from 15% to 22% sodium sulfate and from 5% to 12% zinc sulfate. Other metal sulfates such as iron, manganese, nickel and the like may be present and may replace some of the zinc sulfate. The temperature of the spinning bath may vary from about 25 C. to about 80 C., though at the lower temperatures the higher concentrations of sodium sulfate cannot be used because of the difficulty of solubility. However, at the preferred temperatures of between about 45 C. to about 70 C., solubility is no problem. In the production of the all skin and thick skin types of filaments, the temperature of the spinning bath is not critical. However, as is well known in the conventional practice in the art, certain of the physical properties such as tensile strength are affected by the temperature of the spinning bath. Thus, in the production of filaments for tire cord purposes in accordance with the method of this invention, the spinning bath is preferably maintained at a temperature between about 55 C. and 65 C. so as to obtain the desired high tensile strength.

The acid content of the spinning bath is balanced against the composition of the viscose. The lower limit of the acid concentration, as is well known in the art, is just above the slubbing point, that is, the concentration at which small slubs of uncoagulated viscose appear in the strand asit leaves the spinning bath. Though for any given spinning conditions, a substantially higher percentage of skin will be obtained through the use of the additives of the present invention, in order to get an all skin yarn, the carbon disulfide content of the viscose should preferably be at least 35% based on the dry cellulose. Also, the acid content of the spinning bath should preferably not exceed about 11% while the zinc sulfate should preferably be within the range of 5% to 12%. However, frequently in commercial spinning practice, it is desirable to have a somewhat higher acid content in the spinning bath. It has been found that higher acid contents can be used for any given amount of additive and still exceptionally high skin and all skin yarns obtained if the carbon disulfide content of the viscose is increased and the Zinc sulfate content of the bath maintained at a reasonable high level such as above 8.0%. Thus, even though in practicing the present invention for the production of all skin products, it is generally preferred that the acid concentration of the bath not exceed about 11%, all skin products will be obtained at higher acid concentrations up to as high as about 14% if the carbon disulfide content of the viscose is sufficiently increased and the zinc sulfate of the spinning bath is not appreciably below about 10%. Of course, increasing the amount of additive, within the range specified, also permits, to some degree, the use of higher acid concentrations in the spinning bath. As a general rule, it can be stated, in practicing the present invention with the additives mentioned, that if difficulty is encountered in obtaining a skin product because of the desire to use a spinning bath having an acid content in excess of 11% somewhat higher acid contents can be used by employing a viscose of higher carbon disulfide content and by increasing the zinc sulfate content of the bath within the limits indicated.

Though various terminology may be used to indicate the point at which the viscose is sufficiently coagulated to permit uniform withdrawal from the spinneret, for purposes of the present application, the term slubbing point will be used. This lower acid concentration is readily determined by those skilled in the art through observance of the filaments as formed and has no particular effect on the production of high skin or all skin products in practicing the present invention. In general, the lower limit of sulfuric acid required in order to give sufficient coagulation for spinning, for example, with a viscose containing 7% cellulose and 6% caustic, is about 6%. Another way of stating this is that an acid concentration of about 6% is slightly above the slubbing point. It is apparent that for viscose with higher caustic content, a slightly higher acid concentration would be required due to the partial neutralizing effect of the increased caustic.

It is clear from the above that there is a maximum acid concentration for any specific viscose composition of given carbon disulfied content beyond which substantially all skin products will not be obtained with the present additives. It is also clear that this maximum acid concentration can be somewhat increased through the use of higher concentrations of Zinc sulfate in the spinning bath and by increasing the carbon disulfide content of the viscose. For example, in general, the acid concentration of the spinning baths which are satisfactory for the production of all and substantially all skin products from a 7% cellulose, 6% caustic, 3'5% carbon disulfide viscose containing the above mentioned ethylene diamine derivatives, lies between about 6% and about 8.5%. The acid concentration may be increased as the amount of additive is ncreased and also as the salt test of the viscose is increased. There is an upper limit, however, for the acid concentration based upon the amount of modifier and the concentration of caustic in the viscose. All skin prod ucts cannot be obtained if the acid content of the bath is increased above the maximum value even though the amount of added modifier is increased to as much as 4% while other conditions are maintained constant. For example, a viscose containing about 7% cellulose, about 6% caustic soda, about 35% carbon disulfide based on the dry cellulose and 1%, based on the weight of the cellulose in the viscose, of an ethylene oxide adduct of ethylene diamine containing about 50 ethylene oxide units per molecule and having a salt test of 9 to 10 when extruded into spinning baths containing 16% to 20% sodium sulfate, 4% to 8% Zinc sulfate and sulfuric acid of not more than about 8.5%, results in the production of all skin filaments. Lesser amounts of sulfuric acid may be employed. Greater amounts of acid result in the production of products having skin and core. At acid concentrations in excess of 11%, the skin would generally comprise less than about 80% of the filament. By increasing the carbon disulfide content to 50%, however, and increasing the zinc sulfate content of the acid spinning bath to about 10%, the acid concentration of the spinning bath can be increased to as much as about 14% and similar results can be obtained.

It has been determined that the maximum permissible acid content of the bath, in percent, is approximately 0.36 times the percentage of carbon disulfide in the viscose as based on the weight of the cellulose and is preferably maintained between about 0.2 and 0.25 times the percentage of carbon disulfide as based on the weight of the cellulose. It is also generally preferred that the acid content of the spinning hath not exceed about 1.4 times the caustic soda content of the viscose for the production of all skin products.

It has been further discovered that the acid concentration, in percent, may be increased to about 1.6 times the percentage of caustic soda in the viscose, for example, to about 9.6% for a 6% NaOH viscose, if a small proportion such as at least about 0.02%, preferably between about 0.05% and about 0.15%, of an alkylene oxide adduct of ethylene diamine is present in the spinning bath in addition to the modifier present in the viscose. The adduct dissolved or dispersed in the spinning bath is of the type described hereinbefore and is preferably the same as that incorporated in the viscose because some of the adduct will be leached from the viscose at it is extruded or spun into the spinning bath.

The presence of the adducts or ethylene diamine derivatives in the viscose or in the viscose and the spinning bath retards coagulation and, therefore, the amount of adduct employed is preferably reduced at high spinning speeds. Thus, for optimum physical characteristics of an all skin yarn formed from a viscose as above and at a spinning speed of about 50 meters per minute, the adduct is employed in amounts within the lower portion of therange, for example, about 0.5%. The determination of the specific maximum and optimum concentration of acid for any specific viscose, spinning bath and spinning speed is a matter of simple experimentation for those skilled in the art. The extruded viscose must, of course, be immersed or maintained in the spinning bath for a period suflicient to effect relatively complete coagulation of the viscose, that is, the coagulation must be suificient so that the filaments will not adhere to each other as they are brought together and Withdrawn from the bath.

In the production of filaments for such purposes as the fabrication of tire cord, the filaments are preferably stretched after removal from the initial coagulating and regenerating bath. From the initial spinning bath, the

filaments may be passed through a hot aqueous bath which may consist of hot water or a dilute acid solution and may be stretched from about 70% to about 120%, preferably between and Yarns for other textile purposes may be stretched as low as 20% and may be stretched in air, if desired. The precise amount of stretching will be dependent upon the desired tenacity and other properties and the specific type of product being produced. It is to be understood that the invention is not restricted to the production of filaments and yarns but it is also applicable to other shaped bodies such as sheets, films, tubes and the like. The filaments may then be passed through a final regenerating bath which may contain from about 1% to about 5% sulfuric acid and from about 1% to about 5% sodium sulfate with or without small amounts of zinc sulfate if regeneration has not previously been completed.

The treatment following the final regenerating bath, or the stretching operation where regeneration has been completed may consist of a washing step, a desulfurizing step, the application of a finishing or plasticizing material and drying before or after collecting, or may include other desired and conventional steps such as bleaching and the like. The treatment after regeneration will be dictated by the specific type of shaped body and the proposed use thereof.

Regenerated cellulose filaments prepared from viscose containing the small amounts of the water-soluble or water-dispersible alkylene oxide adducts of ethylene diamine and spun in the spinning baths of limited acid content or from viscose containing the adducts and higher acid baths containing the adducts have a smooth or noncrenulated surface and have an enhanced proportion of skin and under certain conditions consist substantially entirely of skin. Because of the uniformity of structure throughout the filament, the swelling and staining characteristics are uniform throughout the cross-section of the filament. Filaments produced pursuant to this invention and having at least about 80% skin or consisting entirely of skin have a high toughness and. a greater flexing life than filaments as produced according to prior methods which may attributed by the uniformity in skin structure throughout the filament. Although the twisting of conventional filaments, as in the production of tire cord, results in an appreciable loss of tensile strength, there is appreciably less loss in tensile strength in the production of twisted cords from the filaments consisting entirely of skin. Filaments prepared in accordance with this invention have a high tensile strength as compared to normal regenerated cellulose filaments, have superior abrasion and fatigue resistance characteristics and have a high flex-life. Such filaments are highly satisfactory for the production of cords for the reinforcement of rubber products such as pneumatic tire casings, but the filaments are not restricted to such uses and may be used for other textile applications.

It is obvious that the adducts may be added to the lower-acid content spinning baths, if desired. In such instance, it is also essential to maintain the amounts of the adduct in the viscose and the composition of the spinning bath Within the stated limits. The thick-skinned and all skin products of improved properties are obtained only when the spinning operation in the presence of the alkylene oxide adducts of ethylene diamine is carried out within the spinning bath composition range as set forth hereinbefore.

The invention may be illustrated by reference to the preparation of regenerated cellulose filaments from a viscose containing about 7% cellulose, about 6% caustic soda, and having a total carbon disulfide content of about 41% based on the weight of the cellulose. The viscose solutions were prepared by xanthating alkali cellulose by the introduction of 36% carbon disulfide based on the weight of the cellulose and churning for about 2 /2 hours. The cellulose xanthate was then dissolved in caustic soda 7 solution. An additional carbon disulfide was then added to the mixer and the mass mixed for about one hour. The viscose was then allowed to ripen for about 30 hours at 18 C. In those instances where the modifier was incorporated in the viscose, the desired amount of an ethylene oxide adduct of ethylene diamine was added to the solution and mixed for about /2 hour before allowing the viscose to ripen. In these specific examples, the adduct contained about 50 ethylene oxide units per molecule of ethylene diamine.

In the examples summarized in the table which follows, the adduct was incorporated in the viscose and in Examples 3 and 4 a small amount of the adduct was also dissolved in the spinning bath.. The percentage of adduct set forth in the table is expressed as percent by weight of the cellulose in the viscose and of the bath. The viscose was extruded through spinnerets to form filaments which were then stretched in a bath of hot water and collected in spinning boxes. The filaments were subsequently washed free of acids and salts and dried.

The-filaments of Examples 1, 2, 3 and 4 had smooth, non-crenulated surfaces and consisted entirely of skin. The filaments of Example 5 (control) had a very irregular and serrated surface and consisted of about 75% skin and the balance core with a sharp line of demarkation between the skin and the core.

Example 1 2 3 4 5 Percent Adduct 1 1 1 2 None Viscose:

Salt Test 10.8 10.8 10.8 9. 5 Percent Cellulose. 7 7 7 7 7 Percent NaOH 6 6 6 6 6 Percent CS2 41 41 41 41 41 Spinning Bath:

Percent H2804 7. 2 8 8.8 8. 8 7. 6 Percent ZnSO4 8.4 8.4 8.4 8.4 8 Percent NazSO4 20 20 20 20 18 Temperature, O 60 60 62 63 61 Percent Adduct None None 0.1 0.1 None Stretch Bath:

Temperature, C 97 95 95 95 95 Percent Stretch.. 82 82 82 82 82 Spin Speed 1 22 22 22 22 22 Denier 210 215 205 210 210 No. of filaments. 120 120 120 120 120 Tenacity, Dry 2.9 3. 5 3. 5 3. 5 2.8 Tenacity, Wet 2.0 2. 8 2. 8 2. 7 2.1 Elongation, Dry, percen 19 21 22 23 21 Elongation, Wet, percent 24 28 29 3O 27 Percent Skin 100 100 100 100 75 1 Spinning speed expressed as meters per minute. i Tenacity expressed as grams per denier.

Example 6 Approximately 1% (based on the weight of the cellulose) of the ethylene oxide adduct of ethylene diamine was added to and incorporated in the viscose as described above. The viscose employed in the spinning of filaments had a salt test of 10. The viscose was extruded through a spinneret to form a 1650 denier, 720 filament cord at a rate of about 21 meters per minute. The coagulating and regenerating bath was maintained at a temperature of about 60 C. and contained 7.2% sulfuric acid, 8% zinc sulfate and 17% sodium sulfate. The cord was stretched about 90%, washed free of acids and salts by treatment with water at about 95 C. on thread advancing reels, dried and collected on cones.

The individual filaments have a smooth, non-crenulated exterior surface and consist entirely of skin, no core being detectable at high magnification (e.g. 1500 The filaments of a control yarn spun with the same viscose but without the addition of the modified agent and spun under the same conditions, exhibit a very irregular and serrated surface and are composed of about 75% skin and the balance core with a sharp line of demarkation between the skin and core. The filaments had a dry tenacity of 4.5 grams per denier and a wet tenacity of 3.2 grams per denier. The elongation of the dry filaments was 11.4% and of the wet filaments 30.7%.

8 Example 7 A viscose solution as-described above containing 2% of the adduct and having a salt test of 9.5 was spun into a 349 denier, 44 filament yarn by extrusion into a spinning bath containing 9.3% sulfuric acid, 8% zinc sulfate, 20% sodium sulfate and 0.1% of the ethylene oxide adduct of ethylene diamine. The bath was maintained at 62 C. and the extrusion rate was about 25 meters per minute. The filaments were stretched about 57% in air. The yarn was co lected in a spinning box, washed free of acid and salts and dried.

The filaments had a smooth, non-crenulated surface and consisted entirely of skin while control filaments had a very irregular and serrated surface and consisted of about skin and the balance core with a sharp line of demarkation between the skin and core. The filaments had a dry tenacity of 1.8 grams per denier and a wet tenacity of 1.0 gram per denier. The elongation of the dry filaments was 57% and of the wet filaments 42%. Although the strength or tenacity of these filaments was low for some purposes, the filaments had exceptionally high elongation properties.

Example 8 A viscose solution containing 5% cellulose, 8% caustic soda, 38% carbon disulfide, based on the weight of the cellulose, and 3%, based on the weight of the cellulose, of the same ethylene diamine derivative was prepared as described above. The viscose after ripening was spun at a salt test of 14.2 to form an 815 denier, 720 filament cord at a rate of about 25 meters per minute. The coagulating and regenerating bath contained 9.5% sulfuric acid, 8% zinc sulfate and 17% sodium sulfate and was maintained at a temperature of 45 C. After removal from the spinning bath, the filaments were passed through a hot water bath (90 C.) and stretched about 90%. The filaments were washed, dried and collected.

The filaments had a smooth, non-crenulated exterior surface and consisted of about skin with a very diffuse boundary between the skin and core. Filaments formed from like viscose without the ethylene diamine derivative spun under the same conditions exhibit an irregular and serrated surface and consist of 55% to 60% skin with a very sharp line of demarkation between the skin and core. The filaments formed in accordance with this invention had a wet tenacity of 3.48 grams per denier and a dry tenacity of 4.58 grams per denier. The elongation of the filaments was 35.7% for the wet condition and 15.2% when dry.

Although the tenacity and elongation are the only properties set forth, they have been chosen because of the ease and simplicity with which such properties may be determined. In some instances, products made in accordance with this invention do not exhibit large or great improvements in tenacity and elongation, however, the products consist of a smooth-surfaced, all skin structure or have a thick skin structure and possess improved abrasion resistance, flex-life and other properties as disclosed hereinbefore.

One of the properties of viscose rayon which has limited its uses is its relatively high cross-sectional swelling when wet with water, this swelling amounting to from about 65% to about 80% for rayon produced by conventional methods. Rayon filaments produced in accordance with the method of this invention have an appreciably lower cross-sectional swelling characteristic, the swelling amounting to from about 45% to about 60%.

The modifier of this invention may be added to any desired viscose such as those normally used in industry, the specific viscose composition set forth above being merely for illustrative purposes. The alkylene oxide adduct of ethylene diamine may be added at any desired stage in the production of the viscose and may present in the cellulosic raw material although it may be necessary to adjust the amount present to produce a viscose having the proper proportions ofthe adduct at the time of spinning.

i The term skin is employed to designate that portion of regenerated cellulosefilaments which ispermanently stained or dyed by the following procedure: A microtome section of one or more of the filaments mounted in a Wax block is taken and mounted on a slide with Meyers albumin fixative. After dewaxing in xylene, the section is placed in successive baths of 60% and 30% alcohol for a few moments each, and it is then stained in 2% aqueous solution of Victoria Blue BS conc. (General Dyestuifs Corp.) for 1 to 2 hours. At this point, the entire section is blue. By rinsing the section first in distilled water and then in one or more baths composed of 10% water and 90% dioxane for a period varying from 5 to 30 minutes depending on the particular filament, the dye is entirely removed from the core, leaving it restricted to the skin areas. p

This applicationis a continuation-impart of my copending application Serial No. 478,938, filed December 30, 1954, entitled Method of Forming All Skin Viscose Rayon.

While preferred embodiments of the invention have been disclosed, the description is intended to be illustrative and it is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined by the appended claims.

I claim 1. Inamethod of producing'shaped bodies of regenerated cellulose, the step which comprises extruding viscose containing at least 30% carbon disulfide, based on the weight of the cellulose, and from about 0.25 to about 4%, based on the Weight of the cellulose, of an ethylene diamine derivative into an aqueous spinning bath containing from about to 25% sodium sulfate, from about 3% to zinc sulfate and sulfuric acid, the percentage of sulfuric acid in the spinning bath exceeding the slubbing point but not exceeding about 0.36 times the percentage of carbon disulfide in the viscose, based on the weight of the cellulose in the viscose, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about 100 of their respective alkylene oxide units per molecule of ethylene diamine.

2. The step in the method as defined in claim 1 Wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

3. In a method of producing shaped bodies of regenerated cellulose, the step which comprises extruding viscose containing at least about 30% carbon disulfide, based on the weight of the cellulose, and from about 0.25% to about 4%, based on the Weight of the cellulose, of an ethylene diamine derivative into an aqueous spinning bath containing from about 10% to sodium sulfate, from about 3% to 15% zinc sulfate and sulfuric acid, the percentage of sulfuric acid in the spinning bath exceeding the slubbing point but not exceeding about 1.4 times the percentage of caustic soda in the viscose, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about 100 of their respective alkylene oxide units per molecule of ethylene diamine.

4. The step in the method as defined in claim 3 wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

5. In a method of producing shaped bodies of regenerated cellulose, the step which comprises extruding viscose containing at least 30% carbon disulfide, based on the weight of the cellulose, and from about 0.25%

10 to about 4%, based on theweight of the cellulose, of an ethylene diamine derivativeinto an aqueous spinning bath containing from about 10% to 25 sodium sulfate, from about 3% to 15% zinc sulfate, at least about 0.02% of an ethylene diamine derivative and sulfuric acid, the percentage of sulfuric acid in the spinning bath exceeding the slubbing point but not exceeding about 1.6 times the percentage of caustic soda in the viscose, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about of their respective alkylene oxide units per molecule of ethylene diamine.

6. The stepin the method as defined in claim 5 wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

7. In a method of producing shaped bodies of regenerated cellulose consisting substantially entirely of skin the steps which comprise adding to and incorporating in viscose containing at least 35% carbon disulfide, based on the weight of the cellulose, from about 0.5% to about 3%, based on the weight of the cellulose, of an ethylene diamine derivative and extruding the viscose at a sodium chloride salt test of not less than about 9 into an aqueous spinning bath containing from about 10% to 25% sodium sulfate, from about 3% to 15% zinc sulfate and sulfuric acid, the percentage of sulfuric acid in the spinning bath exceeding the slubbing point but not exceeding about 0.36 times the percentage of carbon disulfide, based on the weight of the cellulose in the viscose, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about 100 of their respective alkylene oxide units per molecule of ethylene diamine.

8. The method as defined in claim 7 wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

9. In a method of producing shaped bodies of regenerated cellulose consisting substantially entirely of skin the steps which comprise adding to and incorporating in viscose containing at least 35% carbon disulfide, based on the Weight of the cellulose, from about 0.5 to about 3%, based on the weight of the cellulose, of an ethylene diamine derivative and extruding the viscose into an aqueous spinning bath containing from about 10% to 25% sodium sulfate, from about 3% to 15% zinc sulfate and sulfuric acid, the percentage of sulfuric acid in the spinning bath exceeding the slubbing point but not exceeding about 1.4 times the percentage of caustic soda in the viscose, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about 100 of their respective alkylene oxide units per molecule of ethylene diamine.

10. The method as defined in claim 9 wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

11. In a method of producing shaped bodies of regenerated cellulose consisting substantially entirely of skin the steps which comprise adding to and incorporating in viscose containing at least 35% carbon disulfide, based on the weight of the cellulose, from about 0.5 to about 3%, based on the Weight of the cellulose, of an ethylene diamine derivative, adding to and incorporating in an aqueous spinning bath at least about 0.02% of an ethylene diamine derivative and extruding the viscose into the spinning bath, the aqueous spinning bath containing from about 10% to 25% sodium sulfate, from about 3% to 15% 21 110 sulfate and Sulfuric acid, the perce'ntage of sulfuric acid in the spinning bath exceeding the slubbing point but not exceeding about 1.6 times the percentage of caustic soda in the viscose, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about 100 of their respective alkylene oxide units per molecule of ethylene diamine.

- 12. The method as defined in claim 11 wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

13. The method of producing shaped bodies of regenerated cellulose consisting substantially entirely of skin which comprises adding to and incorporating in viscose containing from 35% to 50%, based on the weight of the cellulose, from about 0.5% to about 3%, based on the weight of the cellulose, of an ethylene oxide adduct of ethylene diamine, adding to and incorporating in an aqueous spinning bath at least about 0.02% of an ethylene oxide adduct of ethylene diamine and extruding the viscose at a salt test of not less than about 9 into the spinning bath, the ethylene oxide adducts containing from about 32 to about 60 ethylene oxide units per molecule of ethylene diamine, the aqueous spinning bath containing from about 15% to 22% sodium sulfate, from about to 12% zinc sulfate and an amount of sulfuric acid to provide a sulfuric acid content exceeding the slubbing point but not exceeding about 11%.

14. A viscose spinning solution containing from about 0.25% to about 4%, based on the Weight of the cellulose, of an ethylene diamine derivative selected from the 12 group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about of their respective alkylene oxide units per molecule of ethylene diamine.

15. An aqueous spinning bath for coagulating viscose solutions containing from about 10% to 25% sodium sulfate, from about 3% to 15% zinc sulfate, at least 0.02% of an ethylene diamine derivative and up to about 14% sulfuric acid, the ethylene diamine derivative being selected from the group consisting of ethylene oxide adducts and propylene oxide adducts of ethylene diamine, the adducts containing from about 28 to about. 100 of their respective alkylene oxide units per molecule of ethylene diamine.

16. An aqueous spinning bath as defined in claim 15 wherein the ethylene diamine derivative is an ethylene oxide adduct of ethylene diamine containing from about 28 to about 100 ethylene oxide units per molecule of ethylene diamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,412 Herzog Apr. 20, 1937 2,284,028 Ubbelohde May 26, 1942 2,359,749 Collins Oct. 10, 1944 2,506,249 Tammen May 2, 1950 2,516,316 Hare July 25, 1950 2,593,466 MacLaurin Apr. 22, 1952 2,884,332 Locher Apr. 8, 1956 2,772,444 Burrows Dec. 4, 1956 2,796,319 Studer June 18, 1957 2,852,334 Hollihan Sept. 16, 1958 2,892,729 Howsmon June 30, 1959 2,904,446 Schlatter Sept. 15, 1959 

1. IN A METHOD OF PRODUCING SHAPED BODIES OF REGENERATED CELLULOSE, THE STEP WHICH COMPRISES EXTRUDING VISCOSE CONTAING AT LEAST 30% CARBON DISULFIDE, BASED ON THE WEIGHT OF THE CELLULOSE, AND FROM ABOUT 0.25% TO ABOUT 4%, BASED ON THE WEIGHT OF THE CELLULOSE, OF AN ETHYLENE DIAMINE DERIVATIVE INTO AN AQUEOUS SPINNING BATH CONTAINING FROM ABOUT 10% TO 25% SODIUM SULFATE, FROM ABOUT 3% TO 15% ZINC SULFATE AND SULFURIC ACID, THE PERCENTAGE OF SULFURIC ACID IN THE SPINNING BATH EXCEEDING THE SLUBBING POINT BUT NOT EXCEEDING ABOUT 0.36 TIMES THE PERCENTAGE OF CARBON DISULFIDE IN THE VISCOSE, BASED ON THE WEIGHT OF THE CELLULOSE IN THE VISCOSE, THE ETHYLENE DIAMINE DERIVATIVE BEING SELECTED FROM THE GROUP CONSISTING OF ETHYLENE OXIDE ADDUCTS AND PROPYLENE OXIDE ADDUCTS OF ETHYLENE DIAMINE, THE ADDUCTS CONTAINING FROM ABOUT 28 TO ABOUT 100 OF THEIR RESPECTIVE ALKYLENE OXIDE UNITS PER MOLECULE OF ETHYLENE DIAMINE. 